Apparatus for coating tubes



July 6, 1948. H. A. LEET ET AL APPARATUS FOR COATING TUBES Filed Feb. 3, 1945 .aff

FT'ORNEY Patented July 6, 1948 OFFICE APPARATUS Foa coA'rING 'rimas Harold Adelbert Leet and Passaic, N. J., assigno Laboratories, Inc., of Delaware Charles Wasko Sectish, rs to Allein B. Du Mont P'i. N. li., a corporation Application February 3, 1945, Serial No. 576,012

8 Claims. (Cl. 9155) This invention relates to a device for coating the inside of tubes along a predetermined surface and to the process of` such coating.

The invention is particularly useful for coating the inside surface o`f cathode-ray tubes and a portion of the neck thereof with electrically conducting material. such as Dlxonac, for example, in a thin layer which is a carbon containing liquid that can be dried to leave a layer. After the material has been introduced with the open end of the tube extending in a downward direction, the liquid is drained out and air is' introduced to dry the layer.

The inventionmay be understood from the description ln connection with the accompanying drawing, in which:

Fig. 1 is a side view illustrating the invention;

Fig. 2 is a longitudinal section partly broken away showing some of the details; and Fig. 3 is a similar view showing some of the parts in a diiierent position.

In the drawing, reference character i indicates a cathode-ray tube which is to be coated on a portion of the inside and a portion of the neck 2 thereof with a liquid coating of electrically conducting material which hardens as a thin film on the inside of the tube after the major portion of the liquid is drained out.

The device for introducing the coating Inaterial and subsequently drying the residual layer of such material is as a whole indicated by the reference character i.

A comparatively large tube d extends into the neck 2, this tube d having an outwardly flaring upper end 5 and a threaded lower end 6.

A metal tube l is located inside of the`tube d with its upper end extending in a liquid-tight manner through a. hole d in the ii-ared end b of the tube d. A liquid hose 9 is connected to the lower end of the tube l.

Another metal tube I0 extends through the tube d and is'provided with an air hose li at its lower end. A cone-shaped baille l2 is fixedly attached to the tube l0 and is of such a size as to leave a. small Iannular space iB between its edge and the inside surface of the neck 2 when the device is in operating position.

A thick walled ring i4 oi rubber or the like surrounds the upper portion of the tube 4l and nts the inside of the neck 2. A nut iii is threaded on the lower end portion 6 of tube 4. Thisnut has a shoulder I8 and a reduced circular portion Hollow disc I8 fits the inside of the neck of the tube 2 and the outside of tube 4 and is integral with a' tubular extension i9 which is of suilciently large diameter to clear or surround the thread 6 on tube 4 and contact with the small end of the nut Ib. t

A baille 20 is attached to the upper end of the tube I0 to divert the air, that is passed through thistube iii, outwardly and downwardly.

The operation is as follows:

The device is inserted into the neck 2, the nut i5 is then screwed up to push the tube I@ inwardly, thus squeezing the rubber ring id into the position shown in Fig. 3. This holds the device in position in the neck of the tube 2. TheA coating material is introduced through hose 9 and tube l, while the tube 'i is held in an upright position, until the liquid reaches the desired level which is determined by the extent to which this tube is to be coated. The hose 9 is then disconnected and the liquid is permitted to drain out through tube l.

Air ls then introduced through the hose ii and tube ill to dry the coating. As this air passes out through the annular space I3 it sweeps the corner at the top outer edge of rubber ring ill and prevents a thickened ring of the material from forming there.

When the coating is dried the nut ib is loosened so that the tube i9 can be returned to the position shown in Fig. 2 so that the device can be removed from the neck 2 and used for coating the next tube.

What is claimedis:

1. A device for coating t-he inside of cathoderay tubes, which comprises a liquid inlet and an air inlet extending respectively into the neck and into the bowl of said tube, a seal for the neck oi' said tube, and a disc shaped baille in the neck of said tube having an outwardly and downwardly extending upper surface with the rim of said baille near the inner surface of the neck of said tube.

2. A device for coating the inside of cathoderay tubes, which comprises a liquid inlet and an air inlet extending respectively into the neck and into the bowl ofsaid tube, a seal for the neck of said tube, and a baille in the neck of said tube having all portions of its rim spaced from but in vclose proximity to the inside surface of the neck of said tube. l

3.v A device for coating the inside of cathoderay tubes, which comprises a liquid inlet and an j air inlet extending respectively into the neck and into the bowl of said tube, a seal for the neck of said tube, and a baille in the neck of said tube having a rim in close proximity to but spaced from the inside surface of the neck of said tube, said baille being located close to said seal.

4. In a device of the character described, a seal for the neck of a tube, a tube located away from the wall of said neck for introducing coating material into said tube and withdrawing the same, and a bae located near the inner end of said coating material tube with its edge in close proximity to the inside wall o! the neck of said tube.

5. The device of claim 4. in which said seal is located near said baule'.

6. A device for coating the inside of a cathoderay tube, which comprises a liquid inlet tube and an air inlet tube terminating respectively in the neck and bowl of said cathode-ray tube, a larger tube surrounding a portion of said liquid inlet and air inlet tubes and having a conically shaped upper end and a threaded lower end, a nut on said lower end, a still larger tube supported on said nut and having a disc at its upper end through which said larger tube and said liquid inlet and air inlet tubes extend, a rubber disc in the neck of said cathode-ray tube between said 4 cgiically shaped upper end and said rst named 7. 'I'he device of claim 6 in which a baille is located in the neck of said cathode-ray tube above said tube that has a conically shaped upper end.

8. The device of claim 6 in which a baille is supported by said air inlet tube in the neck oi said cathode-ray tube.

HAROLD ADELBERT LEET. CHARLES WASKO QECTISH.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,077,378 Deren Apr. 30, 1937 2,096,416 Weinhart Oct. 19, 1937 2,151,649 Birdseye et al. Mar. 21, 1939 2,303,290 Michael Nov. 24, 1942 2,317,977 Casellinl May 4, 1943 2,375,482 Lyle May 8, 1945 

